The present invention relates generally to the illumination of panel mounted aircraft cockpit instruments or the like. More particularly, in a preferred embodiment thereof, the present invention provides infrared light-filtered, easily removable instrument illuminating apparatus having significantly improved bulb support and heat dissipation characteristics.
Aircraft cockpit instruments, such as altimeters, compasses and the like, are typically illuminated for low light flying conditions by a series of small incandescent bulbs operatively mounted on the instrument panel adjacent the instruments to which they provide light. It is quite well known that the infrared light radiation generated by an illumination system of this general type seriously interferes with the use of night vision equipment such as night vision goggles worn by pilots and used to detect the infrared and near infrared signatures, even in total darkness, of target and reference objects on the ground. To alleviate this interference with night vision equipment, various types of infrared filter structures have been used in conjunction with the bulbs to shield the cockpit area from the infrared light radiation which they unavoidably generate.
Of necessity, the shielding of the bulbs with an infrared filter structure, particularly when each bulb is imbedded or encapsulated, traps a considerable amount of heat closely adjacent each bulb, thereby undesirably elevating its operating temperature and significantly reducing its operating life. Accordingly, conventional filtered bulbs must be rather frequently removed and replaced.
This bulb burnout problem commonly encountered in conventional night vision instrument illuminating systems is compounded in many instances by the often relatively inaccessible positioning of the bulbs (for example, behind the instrument panel), a mounting feature which often renders the bulb replacement process a laborious and time-consuming one.
In addition to causing the bulbs to overheat and burn out prematurely, conventional mounting systems used to position the bulbs in an illuminating relationship with the instruments often transmit to the rather delicate bulb filaments an undesirably high level of shock and vibration, thereby mechanically shortening the operating lives of the bulbs.
It can readily be seen from the foregoing that a need exists for improved aircraft instrument illuminating apparatus which is compatible with cockpit night vision equipment and eliminates or minimizes above-mentioned and other problems, limitations and disadvantages commonly associated with conventional instrument illumination systems of the general type described. It is accordingly an object of the present invention to provide such improved apparatus.